The use of solar energy in the operation of air conditioning apparatus is disclosed, for example, in U.S. Pat. No. 4,011,731, granted Mar. 15, 1977. The use of an internal combustion engine as a source for both shaft work, to drive, for example, the compressor of air conditioning apparatus and heat to be used, for example, to regenerate the desiccant of air conditioning apparatus, has also been suggested, for example in U.S. Pat. No. 3,401,530, granted Sept. 17, 1978.